Pulse generator



Feb.17,1948. W.N.DEAN 2,435,958

PULSE GENERATOR Filed Aug. 19, 1943 INVENTOR Y WALTER N. DEAN www ORNEY Patented Feb. 17,V 1948 PULSE GENERATOR Walter N. Dean, Larchmont, N. Y., assgnor to The Sperry Corporation, a corporation of Dela- Ware Application August 19, 1943, Serial No. 499,213 1o claims. (c1. 25o-27)v My invention relates to circuits for electric discharge devices and pulse generators.

An object of my invention is to provide means for frequency multiplication and for synchronization of pulses of diiferent frequencies.

Another object of my invention is to provide improved peaked wave generators and to provide for equalization of successive pulses.

In certain types of object locating systems of the pulsed radio beam type, separate Oscilloscopes are employed for indicating range and indicating azimuth and elevation to facilitate tracking of moving objects. In such systems were azimuth and elevation tracking is accomplished by pip matching in the azimuth and elevation oscilloscopes, the range oscilloscope may be provided with a higher sweep frequency than the azimuth and elevation Oscilloscopes. In order to avoid jitter or unsteadiness of the indications, it is essential that sweep Wave sources for all the oscilloscopes be precisely synchronized, although operating at different frequencies. It is accordingly an object of my invention to provide an improved trigger pulse former and provide means `whereby trigger pulses or waves of different frequencies may be produced in exact synchronism.

Other and further objects and advantages will become apparent as the description proceeds.

In carrying out my invention in a preferred form thereof, I utilize a common generator for producing alternating current establishing the 'frequency of low frequency pulses, and for controlling means producing higher frequency pulses which have a frequency which is a multiple of the lower frequency. To this end a polyphase source is utilized and one phase thereof serves to supply the low frequency pulses whereas the phase outputs are combined in an electronic cir cuit to produce the multiple frequency. Electric discharge devices such as vacuum tubes are provided with input circuits coupled to the several phases of the polyphase generator and with outfput circuits coupled to a pulse-forming stage for producing separate peaks or spikes of the same polarity for each positive or negative peak of each phase of the polyphase alternating current source.

A better understanding of the invention will be .afforded by the following detailed description,

considered in connection with the accompanying drawing, in which:

Fig. 1 is a circuit diagram of one embodiment 'of my invention;

Figs. 2, 3, and 4 are e, series of graphs illustrating the wave forms produced at various points in the circuit of Fig. 1; and

Fig. 5 is a circuit diagram of another embodiment of my invention. Y

Like reference characters are .utilized throughout the drawing .to designate like parts.

Since conventional means may be employed for producing pulses at the frequency of a sine wave supply or synchronizing source, and my invention is not primarily concerned with the production of pulses of the same frequency as .the sine wave source, I have not illustrated the apparatus for producing the lower frequency pulses, but have illustrated only a trigger pulse former for producing trigger pulses having a frequency which is a multiple of the frequency of an alternating current supply generator and which may be utilized for synchronizing an oscillator of any suitable type such as a blocking oscillator, for example, which vmay be utilized for producing pulses of the desiredwave shape and the desired multiple frequency. The mul"- tiple-frequency trigger pulse former illustrated in Fig. 1 comprises a polyphase generator shown as a two-phase or quarter-phase alternator I I', a pair of clipping stages I2 and I3, and a series;- connected pulse-forming or peaking stage I4.

The arrangement shown by way of illustration is for the purpose of producing pulses having four times the frequency of the alternating current power supply energizing the lower frequency pulses, and accordingly a, two-phase or quarterphase alternator II is utilized. It will be understood, however, that if a dierent multiple of the lower frequency is to be produced, a supply alternator will be provided having a different number 4of phases such as a three-phase generator, for example, in case a frequency six times the. lower frequency is desired,` or three times the lower frequency in case alternate pulses are eliminated. The alternator II is illustrated schematically as comprising a conventional rotating-field lmachine having a suitable rotor I 5 and output or armature windings I6 and I1 producing voltages out of phase. y

The current supply for the low frequency pulse circuit (not shown) may be taken from oneof the phases, for example, the phase I6 of the alternator II by means of a pair of terminals I8; or a separate single-phase alternator driven `from the same shaft as thealternator II- may be provided lf preferred. Y For the multiple frequency trigger pulse forma,- tion one of the'phases, such as the phase I1, 'is coupled to one clipping stage I2, and the other phase I6 is coupled to the other clipping stage I3. Since the clipping stages and the couplings are similar, only one of them will be described in detail. As illustrated, the stage I2 comprises an electric disch-arge device which may be in the form of a triode vacuum tube having an anode I9, a cathode 2|, and a control electrode or grid 22. The control `electrode 22 is coupled to the phase or output winding I1, preferably through a coupling condenser 23 and a grid-current limiting resistor 24.

The clipping stages I2 and I3 are operated with positive bias and an adjustable source of positive bias voltage is provided comprising aipotentiometer 25 connected to a source of positive voltage or power supply 26 between a positive terminal 21 and a, grounded negative terminal. The por tentiometer 25 has an adjustable tap 28 connected through a bias resistor.v 29 to the input end of the grid-current limiting resistor 24. The anode I9 is connected through a load resistor 3I to the positive terminal 21 ofthe supply source 26.

Corresponding input, biasing and supply connections are provided for thestage I3, which is coupled to the phase I6 Vof the'alternator I I.

The pulse-"forming and clipping stage I4 comprises a pair of electric discharge devices 32 and 33 connected in series to the power supply 26. For the sake of illustration, these devices 32 and 33 are also shown as triode vacuum tubes having, respectively, anodes 34 and 35, cathodes 36 and '31, and control electrodes or'grids 38 and 39. A junction terminal 4I joining the cathode 36 through a bias resistor Vlilto the anode 35 may 4'be connected to an output terminal 42 or serve las the output terminal at which the multiple frequency triggerpulse appears. For producing multiples ofv pulse frequency, the ,control electrodes 38 and 39 are each coupled to both of the ,clipping stages I2 and I3. For example, the control'electrode 39 -o'f the tube 33 is coupled through couplingcondensers 43 and 44 vtothe anodes ofthe stages -I2 and I3 respectively, Aand the resistor-45 is connected betweenthe grid 39 `and the ground or Vnegative terminal :of the supply source 26 for zero-biasing the discharge tube 33. A resistor '48 maybe shunted'around Athe tube 32 toact as an'auxiliary plate load for the tube 33.

The control electrode 38 o'fthe dischargetube 32 is also coupled to the stages I2 and I3 through condensers 46 and 41, but in this casethe control electrode 33 is negatively biased. Such negative bias may be provided by means of aresistor 49 interposed in the cathode lead 'ofthe tube 32 between the cathode 36 and the junction terminal 4l. The resistor 49 is by-passed by a condenser I for preventing A.-C. degeneration. `A conventionalgrid leak resistor 52 ispreferably provided.

.It will be understood that the 'alternator II .supplies output waves which may be substantialfly 'sine waves, although not necessarily so for proper 'operation of my apparatus. Owing to the lfact that the 'stages Ai2 and I3 are positively biased, they carry maximum current with zero input or with positive input Afrom the phase windings I6 and I1. The design of the generator II 'is such and the magnitude of the bias `-is so adiusted that thenegative half-cycles of voltage of lthe Awindings vIt and I1 are suiiicien't to drive the Stages -I 2 and I3 Ywell beyond negative cu`toff. By making the voltage output of the alternator III considerably greater than Vthe vcut-oir voltage of 'the stages l2 and 5|3, -the sta-geen and I3 may be considered to become abruptly knon-oonducting or 90 in phase.

The constants of the coupling circuits 43, 44, and 46, 41, 52 are so chosen that their time Vconstants are considerably less than the alternation period of the alternator I I, and accordingly the coupling lcircuits act as differentiating cir- Vcuits. At the grids 38 and 39 of tubes 32 and 33,

respectively of Fig. l, therefore, peak voltages or pulses appear, corresponding to the steep sides of the square waves A and A of Fig. 2, as illustrated by the curves B and B'gin Fig. 3. It will be observed that negative peaks are produced corresponding to the trailing edges of the square waves of Fig. 2. For clarity, the curves produced `by the phase Il of the alternator II are shown in full lines in Fig. 2 and those produced by the phase I6 are shown in dotted lines in Figs. 2, 3 and 4.

Referring to Figs. 2 and 3, it willbe observed that four peaks or spikes 53, 54, 55,56 are produced for each complete cycle in one ofthe curves of Fig. 2. However, alternate pairs of spikes have opposite polarities. The series-connected stage I4 is provided for reversing the polarity of alternate pairs of spikes for producing an equal num-'- ber of positive spikes as illustrated in Fig. 4, The tube 33 is operated at zero bias in order that a large percentage of the power supply'voltage 26 vill appear across the load impedance of the tube 3- If .the tube 32 Ais regarded merely as 'an anode resistor for the tube 33, or if the shuntlng load resistor 48 alone is considered, it will be apparent that the tube 33'will act las an inversion circuit, invertingv the negative peaks 53 and 54 of Fig.'3 to produce corresponding positive peaks 51 and 58 (Fig. 4). The positive .peaks yapplied to the grid 39 of tube 33 will be lost, however, in the output,

` owing to the fact that the tube 33 iszero biased,

causing the tube 33 to'conduct'current even when there is no input voltage.

The tube 33 may, however, be regarded as a cathode resistor for the tube 32 andaccordingly the positive peaks 55 and 56 supplied to the grid 38 of the tube 32 are reproduced at the output terminal 42 in the manner of a cathode follower stage.

The relativevamplitude of-the peaks lpassed by the tube 32 as a cathode follower stage tends to be less than the relative amplitude of the peaks passed by the tube 33 'as a-resistance kcoupled amplifier stage, and accordingly the time constant of the couplingfcircuit'46, 41, 52 is preferably made greater than that of the coupling cir cuit 43, -44 45 in order that the rdifference in .amplification factors of the tubes 32 and 33 will be kcompensated and all the peaks C of Fig. 4 will have substantially the same amplitude. Y

If desired, a push-pull ltype of .connectionmay be provided for the vacuum tube stages controlled bythe output windings I6 .and I1 .of the .alternator I I. For example, as illustrated in Fig. 5,. a pair of push-pull-connected twin triode clipping stages 46I and 62 may be provided which are coupled through transformers 63 and 64 to 'a source of pclyphase alternating current such as the output windings I6 and I 1 of the alternator IlV of Fig, l, Preferably the transformers 63 and 64 4stats-1 are of the peakingtype suchashsaturable-core peaking transformers" for example. If desired, the vcoupling transformers 63 and 64 may have their primary windings by-passed by condensers i and 68.to eliminate radio frequency input to the windings of the alternator Il. The twin triodes 5i? and 62 have common anode connections through an anode resistor 81to the power supply 26-so as to serve as anode mixer. In this case, the triodes 6| land 62 are negatively biased by means of a negative voltage source 68 connected through a resistor 69 tosecondary transformer midtaps 1| and 12, which are connected also through a grid leak resistor 13 to the cathodes of the triodes 6l and 62. The opposite ends of the secondary winding 14 of the transformer $3 are connected to control electrodes or grids 15 and 16 of the triode units of the twin tube BI and likewise the transformer 64 has a secondary winding connected to corresponding grids of the twin triode 62.

For differentiation of the output of the mixing stages 6| and 62, a differentiation circuitA is provided, comprising a condenser 11 in series with a pair of resistors 18 and 19. For amplification and inversion two additional stages of discharge tube amplification are provided, which may take the form of a twin triode 8l having an initial stage unit with a control electrode 82 connected to the junction terminal 83 of the differentiating circuit 11, 18`and having a negative bias provided by a source of negative voltage 84 connected through a grid leak 85 to the junction terminal 8B of the resistors 18 and 19. The second unit of the twin triode 8| is resistance-capacitance coupled in the conventional manner to the anode 81 of the first unit and the anode 88 of the second unit serves as the output terminal.

Owing to the negative bias of the twin triodes 8| and 62, these tubes are normally non-conducting and their anodes are at the full positive voltage of the supply source 26. However, each peak of each polarity of each phase I6 and i1 produces a voltage dip in the anode voltage source to form an output wave having the form illustrated by the square-topped wave 88, which has a pulse frequency four times that of the frequency of the alternating current input to the tubes 8i and 62. The trailing edges of the negative pulses in curve 89 are sharper than the leading edges owing to the characteristics of the peaking transformers 63 and G4.

The differentiating circuit 11, 18, 19'converts the wave 89 into a wave consisting of alternating positive and negative spikes represented by the wave form 8l. The positive pulses or spikes are sharpest and the largest and these are amplified in two stages. The frequency of the wave 9i equals that of the wave 89. Since the first stage o'f the twin triode 8l is negatively biased, the negative peaks of the wave 9i are eliminated and only the positive peaks are passed, and, being inverted, produce the wave form 92 at the anode 81. The second stage of the twin triode 8| reinverts the wave 92 to form the output wave form 93 at the anode 88. The wave 93 has four positive peaks for each cycle of the input voltage to the tubes 8l and 82.

I have herein shown and particularly described certain embodiments of my invention and certain methods of operation embraced therein for the purpose of explaining its principle of operation and showing its application, but it will be obvious to those skilled in the art that many modifications and variations are possible, and I 6: aim, therefore, to ov'er'ilall such modifications`nr and`variations as fall within the Ascope of my irl-JV vention which is defined in the appended claims.` What is claimed is: 1. A trigger pulse former comprising a sourcei of alternating current with two phasesQa iirst pair of electric discharge'devices having 'their cathodes joined and eachfwith a control electrode coupled to oneof said phases, and a second pair of electric discharge devices in series with a power supply, each of said second pair of discharge de-" vices having a control electrode coupled to each of said first pair of discharge devices, said second pair of discharge devices'having a 'junction terminal serving as an output terminal for trigger pulses. y A 2. A trigger pulse former comprising a source of alternating current with a plurality of phases. a plurality of electric discharge -devices having their cathodes joined and each with a control electrode coupled to one of said phases, and a pair of electric discharge devices in series with a power supply, each of said pfair of discharge devices' having a control electrode coupled to each of said plurality of discharge devices,said pair of discharge devices vhaving a junction terminal serving as an output terminal for trigger pulses.V 3. Apparatus as set forth in claim 2 in which pulse-forming differentiating circuits are provided for coupling said plurality of discharge devices to thel control electrodes of said pair of discharge devices. 4. A trigger pulse former comprising a source of alternating current with a plurality of phases, a plurality of electric discharge devices each with a control electrode coupled to one of said phases, and a pair of electric discharge devices in series with a power supply having positive and negative terminals, each of said pair of discharge devices having a control electrode with a pulseforxning differentiating circuit coupling it to each of said plurality of discharge devices, said pair of discharge devices having a junction terminal serving as an output terminal for trigger pulses,

' and the coupling for the discharge device at the positive end of the series pair having a greater time constant than the coupling for the other discharge device of the series pair.

5. In combination, a plurality of input connections with means for supplying them with polyphase alternating current, a plurality of electric discharge devices having their cathodes joined and each with a control electrode coupled to one of said connections, and a pair of electric discharge devices connected serially each having a control electrode coupled to each of said plurality of electric discharge devices, and said pair of discharge devices having a junction terminal serving as an output terminal.

6. In combination, a plurality of input connections for supplying polyphase alternating current, a plurality of electric discharge devices each with a control electrode coupled to one of said connections, a pair of electric discharge devices connected serially each having a control electrode coupled to each of said plurality of electric discharge devices, and said pair of discharge devices having a junction terminal serving as an output terminal, one of said pair of discharge devices being biased to have relatively high plate resistance and the other being biased to have relatively low plate resistance.

7. A plurality of input connections with means for supplying polyphase alternating current of a given' frequency, and a plurality of pairs of electric 'discharge devices .each .havingrAt-heir control electrodes coupled inpush-.pu-ll to one oil-said input. connections and a common output connec-y tion for said discharge devices, whereby an routput wave is produced having `a frequency which. is equal to twice the product of said given fre-` quency and the number of said input connections.

y8. In combination, a polyphase source of alternating current providinga plurality of volt ages of substantially xedtphase relations, means responsive to each-of said voltages for producing two output pulses spaced 180 degrees apart during each cycle of each of said voltages, land means for combining the outputs of said pulse-producing; meansto deliver pulses at -a frequency given by the frequency of said source multiplied by double the number of phases of said source.

9. In combination, a two-phase source-.of a1- ternating current providing two voltages .of substantially xed 90-degree phase separation, meansfor producingdistorted versions of said two voltages characterized byrtwo abrupt voltage ohanges'spaced substantiallyV 18,0fdegrees apart during each cycle of eachvofisaid two voltages, and a diffe-rentiatingnetwork coupled to -said distorted version producing means for deriving -output voltage pulses corresponding to the-rates of change of said distorted voltage versions, where by four output-pulses spaced substantially 90 de, grecs apart are produced during each cycle of said alternating current source. Y,

10. In combination, a two-phase source .of alternating current providing two voltages of substantallv xed phase separati@ui,l means res-ponsive'to arst .one :Qfzsa-id voltages for producing two voutput pulses spaced 180 degrees during .each cycle thereof and synchronized with said rst voltage in xed phase relation therewith, grneans responsive to thezsecond of said two voltages for producing two output pulses spaced 180 degrees during each cycle thereof,'said last-named means being-adjustedto produce pulses spaced degrees from the pulses produced by said first means, and means .coupled to said first and second means for combining the outputs of said frst` and second means to deliver uniformly spaced pulses at a frequency quadruple the frequency of said twophase source.

vWALTER. N. DEAN.

REFERENCES CITED 'The following references are of record inthe 

